1. Field of the Invention
The present invention relates to an inspection method and an inspecting apparatus for an objective lens driving device.
2. Description of the Related Art
An objective lens driving device is known which drives an objective lens for applying a laser beam for recording or reproducing information to/from an optical disc (see e.g., Japanese Patent Application Laid-Open Publication No. 2003-16668 (Pages 1 to 3, FIGS. 11 to 12)). In the objective lens driving device, focusing control is performed for correcting focusing displacement of the laser beam on a disc surface by moving the objective lens in the direction perpendicular to the disc surface. The objective lens driving device is used for an optical pickup apparatus for recording or reproducing information to/from the optical disc, for example.
A configuration of an objective lens driving device 1 will then be described with reference to FIG. 11.
A base 10 is a metal plate-shaped base including a magnet 21 and a magnet 22 each in a substantially rectangular parallelepiped shape and a yoke 11 and a yoke 12 each in a substantially rectangular flat plate shape having the magnet 21 and the magnet 22 respectively fixed thereto. Specifically, a pair of the yokes 11 and 12 in the substantially rectangular flat plate shape is so formed on the base 10 as to be opposed to each other in the tangential direction of FIG. 11 (tangential direction of a track of the optical disc (not shown) mounted on a turn table (not shown)) and a predetermined housing portion 90 is so formed as to have an opening for providing a main body portion 30 (an actuator main body portion) of an actuator ACT in between the yokes 11 and 12. The “actuator” refers to a driving device that converts energy into translational movement or rotational movement, for example.
The magnet 21 and the magnet 22 are rectangular-parallelepiped-shaped monopole permanent magnets having polarities different from each other. A back surface 21b of the magnet 21 is fixed to the yoke 11 and a back surface 22b of the magnet 22 is fixed to the yoke 21, such that front surfaces of the pair of the magnets 21 and 22 are opposed to each other across the housing portion 90 on the base 10. For example, a magnetic gap is formed in and around/near the housing portion 90 on the base 10 positioned between the opposed surfaces of the magnets 21 and 22. Bottom surfaces 21a and 22a positioned in the focus direction (direction perpendicular to a surface of the optical disc (not shown) mounted on the turn table (not shown)) of the magnet 21 and the magnet 22 are bonded to top surfaces 10b and 10c of the base 10 with an adhesive. Reference numerals 61 and 62 shown in FIG. 11 denote bonding areas between the magnets 21 and 22, and the base 10.
The actuator ACT includes: for example, a lens holder 31 (holder) that holds an objective lens OBL; substantially linear suspension wires 40 (wires) that elastically support the actuator main body portion 30 including a holder 31, etc. provided with the objective lens OBL, etc., so that the actuator main body portion 30 can move; a support plate 50 to which one ends 42 of both ends 41 and 42 of the substantially linear suspension wires 40 is fixed; locking members 32 that lock the other ends 41 of the both ends 41 and 42 of a plurality of the substantially linear suspension wires 40 on each of two opposed side surfaces 31a and 31b positioned in the radial direction (direction perpendicular to the track of the disc surface) of the holder 31 (e.g., two wires for each of the side surfaces 31a and 31b); tracking coils 33 that drive the actuator main body portion 30 positioned mainly substantially in the radial direction; and a focus coil 34 that drives the actuator main body portion 30 mainly substantially in the focus direction. A space 90a for moving the main body portion 30 of the actuator ACT in the focus direction exists between a rear surface 30a of the main body portion 30 of the actuator ACT and a one-step lowered surface 10a positioned substantially in the center of the base 10 and at a distance in the focus direction from the rear surface 30a of the main body portion 30 of the actuator ACT.
The suspension wires 40 are metal wires elastically supporting the main body portion 30 of the actuator ACT via the locking members 32 and having a function of lead wires for passing electric currents through the tracking coils 33, the focusing coils 34, etc. Specifically, each of the suspension wires 40 is locked at the one end 41 to the locking member 32 with solder flux and is fixed at the other end 42 to the support plate 50 with solder agent, damper material, etc., so as to extend parallel to the base 10. The damper material functions to absorb vibrations such as abnormal vibrations when the main body portion 30 of the actuator ACT is driven/moved.
The support plate 50 is a plate to which the other ends 42 of the suspension wires 10 are fixed. The support plate 50 and the base 10 are fixed with each other via a metal case (not shown), for example.
As above, constituent elements other than the base 10 and the holder 31 in FIG. 11 make up a drive mechanism for driving the holder 31 so as to move the objective lens OBL in the focus direction and the tracking direction.
The bonding areas 61 and 62 are areas for bonding the bottom surfaces 21a and 22a of the magnets 21 and 22 to the top surfaces 10b and 10c of the base 10 with an adhesive agent, however, the adhesive agent may flow out or seep out to the one-step lowered surface 10a substantially in the center of the base 10 opposed to the rear surface 30a of the main body portion 30 of the actuator ACT provided with the holder 31, for example. The adhesive agent may not be applied to the bonding areas 61 and 62 as prescribed and may adhere to the one-step lowered surface 10a substantially in the center of the base 10 opposed to the rear surface 30a of the main body portion 30 of the actuator ACT.
The locking member 32 of the main body portion 30 of the actuator ACT locks the one end 41 of the suspension wire 40 by soldering using solder flux, for example, however, the solder flux may adhere to the one-step lowered surface 10a substantially in the center of the base 10 opposed to the bottom surface 30a of the main body portion 30 of the actuator ACT when performing the above soldering operation.
The other end 42 of the suspension wire 40 is fixed to the support plate 50 using the soldering agent or a damper material, for example, however, the damper material may adhere to the one-step lowered surface 10a substantially in the center of the base 10 opposed to the rear surface 30a of the main body portion 30 of the actuator ACT when performing the above fixing operation.
It is assumed that an adhesive foreign substance such as the adhesive agent, soldering flux, or damper material adheres to the one-step lowered surface 10a substantially in the center of the base 10 opposed to the rear surface 30a of the main body portion 30 of the actuator ACT, as above. In this case, when the main body portion 30 of the actuator ACT is moved for the focusing control such that the rear surface 30a of the main body portion 30 of the actuator ACT is moved closer to the one-step lowered surface 10a substantially in the center of the base 10, the rear surface 30a of the main body portion 30 of the actuator ACT adheres to the one-step lowered surface 10a substantially in the center of the base 10 due to the adhesive foreign substance as above.
Under such a situation, when attempting to move the rear surface 30a of the main body portion 30 of the actuator ACT away from the one-step lowered surface 10a substantially in the center of the base 10, there is a problem that the main body portion 30 of the actuator ACT may not smoothly be moved (the controlled response may not be in a linear form) due to the adhesive foreign substance, and thus, the focusing control may not be performed as intended.
This is not limited to the above adhesive foreign substance, but also in a case where a foreign substance such as dust enters between the rear surface 30a of the main body portion 30 of the actuator ACT and the one-step lowered surface 10a substantially in the center of the base 10, there is the problem that the main body portion 30 of the actuator ACT is not smoothly moved.